The present invention relates to a method of manufacturing a dental implant drill guide. The invention also relates to a method for the reconstruction of an edentulous jawbone.
It is known in the art to secure dental prostheses using dental implants secured in the upper or lower jawbone. It is also known in the art to mount a framework or superstructure to a number of implants, the superstructure being used to evenly support a set of false teeth or denture prostheses. Accurate placement within the jawbone of the implants is a difficult task. In International Patent Application No. PCT/IT94/00059, published 24 Nov. 1994 as WO 94/26200, there is described an adjustable guiding device for positioning dental implants in which it is possible for the dental surgeon to adjust a drill axis for each implant before proceeding to use the guiding device or drill template to guide the surgeon""s drill for the purposes of preparing the drill hole for the implant. The guiding device disclosed in the International publication helps the dental surgeon to decide on the drill axis after viewing radiographic images of the radio-opaque tubular drill guide superposed the bone structure.
In the known prior art, the oral surgeon typically has difficulty deciding on a drill axis for the implants since the ideal position for the implants should be decided with knowledge of the jawbone structure into which the implant is to be inserted, knowledge of the position within the jawbone structure of the nerve tissue, the gum surface and the required position and dimensions of the false teeth or dentures to be supported by the dental implant. Of course, in the conventional manner of selecting the implant axis, the dentist or dental surgeon simply makes a best guess in light of his knowledge of the patient. Of course, this leads, in certain cases, to imperfections in the dental prosthesis. The imperfections may be lack of ideal support, unfavorable angulation of an implant causing a weakness in the implant which may cause failure over time, or a visually perceptible defect in the appearance of the prosthesis.
In the conventional method for the construction of the superstructure, a physical model of the patient""s gums and dental implant heads is prepared on which the superstructure is built manually using molding and other techniques known in the art. The craftsman or technician skilled at manufacturing such dental superstructures takes into consideration the size and shape of the desired dentures to be placed over the superstructure when crafting the same. The procedure for manufacturing dental implant superstructures as is conventionally known in the art is time-consuming and sometimes results in imperfect structures or defects in the visual appearance of the dentures to be placed over the superstructure.
In U.S. Pat. No. 5,401,170 granted Mar. 28, 1995 to Nonomura, there is disclosed a method and apparatus for measuring by camera image the implant heads of the implants in the patient""s mouth for the purposes of cutting a frame on which the prosthetic teeth will be arranged and baked. In the method disclosed, the construction of the frame or superstructure is carried out in the absence of a reference to the shape and position of the patient""s ideal teeth position. Thus, as the dentures or artificial teeth are crafted on the frame or superstructure, care would be required during the manual process to ensure that the position of the teeth on the frame will match the opposed set of teeth in the patient""s mouth.
Known techniques also have the disadvantage of necessitating two separate sessions to install the implants and the superstructure. It would be highly beneficial to be able to prepare the superstructure prior to the surgery so that the implants and the superstructure are installed during the same surgical procedure.
It is a first object of the present invention to provide a method of manufacturing a dental implant drill guide or drill template which will result in a precise and accurate drill guide for selected drill holes.
It is furthermore an object of the present invention to provide a method of manufacturing a dental implant superstructure in which information concerning the position of a plurality of dental implants mounted in a jawbone, the gum surface covering the jawbone and the fixed denture shape is all taken into consideration during the specification of the shape of the superstructure before the superstructure is precision made.
It is yet another object of the present invention to provide such methods which provide better accuracy and faster results than conventional methods.
It is yet another object of the present invention to provide a dental implant drill guide which is precise and easy to use such that drilling of the dental implant holes does not require expert skill and knowledge beyond the skill of basic dental surgery. It is furthermore an object of the present invention to provide tools which will reduce the number of visits a patient needs to make to the dental surgeon in order to have dental implants and a dental implant superstructure inserted.
According to a first aspect of the invention, there is provided a method of manufacturing a dental implant drill guide, comprising the steps of: imaging a jawbone and tissue structure with a reference to a known anatomical reference to produce a three-dimensional computer graphics model; selecting at least one implant drill hole position for at least one dental implant using said model, said position being specified in three dimensions, including a hole termination point and orientation, and being referenced to said anatomical reference, entering at least one set of implant drill hole position coordinates into a computer controlled precision manufacturing device; providing a drill template body having a first surface adapted to overlie a gum surface of the jawbone in a single predetermined position; using said precision manufacturing device to provide a fixed orientation drill guide socket in said template body for each one of said at least one drill hole position with a corresponding position and orientation.
According to a second aspect of the present invention, there is provided a method for allowing the reconstruction of an edentulous jawbone in a single surgical operation, comprising the steps of: a) creating a three-dimensional graphic computer model of a patient""s gum, jawbone and tissue structure, and of a dental prosthesis to be placed over the gum; b) selecting a number of virtual implant drill holes positions for corresponding implants using said model; c) entering data related to the virtual implant drill hole positions into a computer controlled precision manufacturing device; d) providing a rigid drill template body; e) using said precision manufacturing device to provide a fixed orientation socket in said drill template body for each one of said implant drill hole positions selected in step b); f) prior to the surgical operation, using said data on said virtual implant drill hole positions and said precision manufacturing device to make a dental implant superstructure having a number of dental implant abutting flanges interconnected by a bridge in a fixed configuration in which said dental abutting flanges are positioned in accordance with the virtual implant drill hole positions; g) using said drill guide to drill pilot holes in the patient""s jawbone at said virtual implant drill hole positions; h) inserting an implant in each of said pilot holes; and i) installing the dental implant superstructure prefabricated in step f) on the implants inserted in the patient""s jawbone.
In the method of manufacturing a dental implant drill guide according to the present invention, the patient is typically edentured, namely, the patient has had all teeth pulled from the jawbone, and the jawbone has been given time to heal since the teeth were pulled. If the patient decides to proceed with dental implants and the placement of a superstructure for solidly securing dentures over the gum, a period of about 1 month is provided for from the time of pulling any remaining teeth from the jawbone before proceeding with the operation of inserting implants into the jawbone.
A medical image of the jawbone and tissue structure is obtained by using x-ray imaging, MRI or possibly nuclear imaging techniques to produce a three-dimensional computer graphics model which has a reference to the gum surface or some other fixed reference with respect to the patient""s jawbone. Preferably, a radiographic scanner guide is used which is molded to conform to the shape of the patient""s gums and which includes radio-opaque spheres whose positions with respect to the gum surface is known.
The primary advantage of the invention is that the oral surgeon may select the optimum position for dental implants using the three-dimensional computer graphics model of the jawbone and tissue structure. Selection of the drill hole positions using the computer graphics model is transferred to a CNC device for the purposes of providing fixed drill guide sockets in the template body for each one of the drill hole positions or position selected using the computer graphics model. While the model is three-dimensional, it may be convenient for the purposes of selecting the drill hole axis to use a two-dimensional representation of the jawbone and tissue structure, the two-dimensional view being displayed with a user controlled slice angle. Preferably, the dental surgeon will select the position for each implant drill hole, not only to position the implant in the optimum location within the jawbone, but also to result in a position of support which is suitable for supporting the dentures. Therefore, it is preferred to display, in addition to the three-dimensional computer graphics model of the jawbone and tissue structure, the patient""s dentures in the proper spatial relationship with respect to the jawbone and tissue structure. This requires imaging the patient""s dentures or teeth, and possibly gum structure, in addition to the jawbone and tissue structure, in such a way that all images are referenced with respect to one another to be integrated into the same three-dimensional computer graphics model.
While it would be possible to prepare the drill template body and provide it with the drill guide sockets using the CNC device, the drill template body is preferably molded on a physical model of the gum surface into which model the CNC device has previously drilled the desired implant drill holes. The drill holes in the physical model are used to build a mold for the drill guide sockets. This prevents the need to use the CNC device to produce fine details except for the precision drilling of the drill holes.
Imaging of the dentures or teeth to be placed over the gum surface and the imaging of the gum surface can be carried out by using laser camera imaging techniques known in the art. These images are preferably obtained using a physical model of the patient""s gum surface, and the physical model is imaged in such a way that the images can be referenced accurately to the jawbone and tissue structure images.
According to one method of manufacturing the dental implant superstructure, the actual dental implant position data is obtained by taking an imprint using transfers connected to the implants. Preferably, the imprint is taken using the same drill guide with the sockets of the drill guide being large enough to receive the transfers and surrounding imprint material. Preferably, the positions and orientations of the transfers are physically measured along with a reference to the drill guide which will permit the relative positions of the implants to be known with a reference to a standard frame of reference. Using the standard frame of reference, it is possible to generate a computer graphics model of the gum surface, dentures or teeth and dental implants which allows the dental surgeon or technician to select the best shape for the overlying bridge of the superstructure.
According to a further general aspect of the present invention, the implant drill hole positions selected using the computer graphics model can also be used to make the superstructure. By so using the planned implant positions, instead of taking an imprint of the implants inserted in the patient""s jawbone to precisely determine their actual locations in relation to the jawbone, the superstructure can be made prior to the surgical operation, i.e. prior to the insertion of the implants into the patient""s jawbone. This advantageously provides for the installation of the implants and the superstructure in a single surgical operation. This novel approach of creating a superstructure on the basis of the virtual positions of the dental implants selected using the three-dimensional computer graphic model of the jawbone and the dental prosthesis has the following advantages for the surgeon:
no need for taking imprints of the implants to determine their positions in the jawbone;
no need for a second surgical procedure to expose the head of the implants;
improved stability of the implants, as they are immediately interconnected to each other by the superstructure;
improved protection of the implants, since they are better stabilized;
less sessions with a patient, thus, higher profitability;
and the following advantages for the patient:
only one operation and, thus, less traumatism;
accelerated healing because of the protection afforded by the superstructure;
In the case of a fixed dental prosthesis which is implant mounted (i.e. porcelain on metal), the ideal form of the superstructure can be automatically designed using the computer model taking into consideration the form of the laser camera imaged teeth and by subtracting a thickness of porcelain which the technician requires to recreate the shape of the imaged teeth. In the case of a dental prosthesis supported by a superstructure (overdenture), the shape of the superstructure can be automatically determined by taking into account the external shape of the prosthesis and by circulating the superstructure inside the prosthesis, making sure that the necessary thickness of prosthesis material (e.g. acrylic) will be available all around in order to provide a adequately strong prosthesis.
When precision forming the superstructure, it is possible to use various techniques. In one embodiment, the entire superstructure is cut using a CNC milling machine programmed to cut according to the shape data specified using the computer model.